Keep search field visible in long lists

[Anujjoshi3105]

Fixes #147
The search field remains visible at the top of the viewport when scrolling.

[fregante]

Thanks for the PR! However what I had asked is exactly what's needed, not position: absolute

.header {
    position: sticky;
    top: 10px;
    background: gray;
    outline: solid 10px gray;
	z-index: 100
}

Just the values need to be adjusted, for example to use var() for the margin and the color.

[Anujjoshi3105]

Ligth and dark mode working

[fregante]

Thank you!